WATER. 



grating of caftiiron, is fixed on the top of the breaft K, and 

 the Shuttles are applied at the back of the grating E, fo as 

 to Aide up and down againft it, the ftrain occafioned by the 

 prefTure of the water being borne by the grating. The 

 lower (huttle is moved by means of long fcrews, a, which 

 have bevilled wheels, b, at the upper ends, to turn them, 

 by a conneftion of wheel-work with the wheel-work of the 

 mill. The upper fhuttle, A, is drawn up or down by 

 racks and pinions, c, which are turned by a winch, or handle. 

 The bars of the grating E are placed one above the other, 

 like flielves, but are not liorizontal ; they are inclined, fo 

 that the upper furfaces of all the bars form tangents to an 

 imaginary circle of one-third the diameter of the wheel 

 defcribed round the centre thereof. Thefe bars are not 

 above half an inch thick, and the fpaces between them are 

 2^ inches. The bars are of a confiderable breadth, the ob- 

 jed: of them being to lead the water, with a proper flope, 

 from the top of the lower (huttle A to flow upon the floats 

 of the wheel. This difpofition allows the (buttles to be 

 placed at fuch a diilance from the wheel as to admit very 

 llrong upright bars of call iron to be placed between the 

 ■wheel and the (buttles, for the (huttles to bear againft, and 

 prevent them from bending towards the wheel, as the great 

 weight of water would otherwife occafion them to do. 

 Thefe upright bars are very firmly fixed to the ftone-work 

 of the breaft at their lower ends, and the upper ends are 

 fattened to a large timber, D, which is fupported at its 

 ends in the fide walls, and has a trufs-framing applied to the 

 back of it, like the framing of a roof, to prevent it from 

 bending towards the wheel. The upright bars are placed 

 at diftances of five feet afunder, fo as to fupport the (hut- 

 tles in two places in the middle of their length, as well as 

 at both ends ; and large rollers are applied in the (huttle, 

 where it bears againft thefe bars, to dimini(h the friftion, 

 which would otherwife be very great. 



Thefe precautions will not appear unnecelFary when the fize 

 of the work is known. The wheel is 21^ feet in diameter, 

 and 15 feet broad ; the fall of water is 14 feet, when it is at 

 a mean height ; the upper (huttle is 2\ feet high, and 15 feet 

 long ; the lower (huttle is 5 feet high, and the fame length, 

 fo that it contains 75 fquare feet of furface expofed to the 

 preflure of the water : now taking the centre of pre(rure at 

 two-thirds of the depth, or 3^ feet, we find the preffurc equal 

 to that depth of water aftingon the whole furface ; that is, 

 the weight of 3^^ cubic feet of water = 208 lbs. bears on 

 every fquare foot of furface, which is equal to 15,600 lbs., 

 or near 7 tons on the lower (huttle only ; but if we take the 

 two (huttles together, the furface is 112 fquare feet, and 

 the mean prefTure 312 lbs. upon each, or 16 tons in the 

 whole. The wheel has forty float-boards pointing to the 

 centre. The wheel is made of caft-iron. There are two 

 wheels of the dimenfions above ftated, which are placed in a 

 line with each other, and are only feparated by a wall which 

 fupports the bearings ; for they work together as one wheel, 

 and the feparation is only to obviate the difficulty of making 

 one wheel of fuch great breadth as 30 feet, though this is 

 not jmpolfible, for there is a wheel in the fame works 40 feet 

 in breadth, but it is of wood and not in iron, framed in a 

 particular manner, as we (hall foon defcribe. 



Mr. Buchanan's Bucht IVatcr-Wheel fcr alor-j) Fail. We 



have already ihewn, that where water can be made to aft 

 on a wheel by weight, it is mucli more elfeftual than when 

 the fame water is made to aft by impulfe ; and we (hall (hew 

 this more fully in fpeaking of overihot-wheels. 



Where tlie fall is lefs than half the diameter of the 

 wheel, if the buckets are made in the ufual form of the 

 buckets for overfhot-wheels, the difficulty of filling them 



with water, and the (hort time they are able to retain the 

 water, are fuch great defefts, that in fuch cafes breaft- 

 wheels, with open float-boards, fuch as we have defcribed, 

 have been found in pradlice to be more advantageous tlian 

 bucket-wheels. 



Mr. Buchanan fuggefts, that, by adopting another form 

 of the buckets, they might be 10 made as to be eafily filled, 

 and at the fame time capable of retaining the water in a 

 fituation to produce nearly its full effeft altogether by 

 weight, on a low fall. 



In a wheel of this conllruftion, contrary to the ufual 

 practice, the water muft be poured into the buckets from 

 within the circle of buckets inftead of from without the cir- 

 cle of buckets. How the filling of the buckets from with- 

 in can be accomplilhed may not at firft be obvious ; but it 

 may be done without the pentrough, which fupplies the 

 water, making any interference with the arms of the wheel, 

 if it is conftrudted as (hewn mjigs. 4. and 5. Piatt I. Water- 

 wheels. Fig. 4. is an horizontal fection of the wheel, and 

 plan of the pentrough ; and Jig. 5. an elevation of the 

 water-wheel. 



The buckets in the figure, empty themfelves by means of 

 apertures on the outfide of the wheel, which arc the whole 

 length of the buckets, but no wider than juft fufBcient to 

 difcharge the water from the buckets when they arrive at 

 the bottom of the wheel, and before they begin to afcend. 

 A A is the pentrough, into which the fupply of water is 

 condufted. From B to C a part of the wheel is reprefented, 

 with the (hrouding removed, to (hew the form of the 

 buckets, and the fituation of the water in them ; a, a, a, are 

 the apertures by which the water efcapes from the buckets ; 

 b the aperture by which the water enters from the pentrough 

 to the buckets. The plan,_yf^. 4., (hews, that the arms, N N, 

 of the wheel, and the circular rims which fupport the 

 buckets, occupy only a fmall part of the breadth of the 

 circular ring of buckets M ; fo that about one-third of the 

 length of the buckets at each end is expofed on the infide 

 of the circle, and againft thefe parts the penftock is applied, 

 as (hewn at A A, and the arms and rim of the wheel, move 

 clear of it ; but the buckets, as they pafs, receive water, 

 which flows in a continual ftream at the orifices, b, b, of the 

 pentrough ; the buckets there become filled from the infide. 

 The partition-boards or plates which form the buckets are 

 reprefented by the white hnes in Jig. 5., and are fo (haped, 

 that they will retain nearly the whole of the water until they 

 arrive at the loweft a ; the water then begins to efcape, and 

 by the time that each bucket arrives at the loweft point of 

 the wheel, it will have difcharged all the water, and will rife 

 up empty. 



This is a truly ingenious contrivance ; but we fear that in 

 the execution it would prefent many difficulties, particularly 

 the ring of buckets M, which could not, we think, be fo 

 firmly afSxed, fupported by the narrow bearing of the two 

 rings and arms N, as to preferve their circular figure for 

 any great length of time ; and any bending or warping of 

 fuch a heavy mafs as a water-wheel will foon deftroy it. 

 Neither is the advantage which could be derived from re- 

 ceiving the water in clofe buckets, inftead of open float- 

 boards, fo great as is generally imagined. 



On the Power and EJfed of Breajl-iuheels. — We (hall 

 fully examine the different effefts of the power of water, 

 when afting by its impulfe and by its weight, under the 

 title of overjloot-wheels. In breaft-wheels of the common 

 conftruftion, the effefts of iuipuUe and weight are com- 

 bined ; but what is there defcribed being carefully attended 

 to, the application of the fame principles in thefe combined 

 cafes will be eafy. 



AU 



